Zetix is a remarkable fabric from Auxetix Ltd; it can resist multiple bomb blasts without tearing. It is a member of a class of fabrics called auxetics that actually become thicker when stretched out.
The idea that a material could become thicker when stretched out is contrary to our usual experience with objects that stretch. For example, a plain bungee cord will indeed get thinner when stretched. However, if you entwine it with a stiffer cord, and then stretch out the two together, the stiffer white-colored cord becomes taut, while the bungee cord wraps around it. The pair of cords are thicker (see illustration).
Now, imagine a fabric that uses this same principle at a much smaller level; when you stretch the fabric, it actually thickens up.
When this principle is applied to protective fabrics, the results are dramatic. Most blast-resistant materials fail when exposed to the energy of a explosive blast. However, the Zetix material thickens to resist the blast, and then returns to its earlier state (see example).
This kind of material has a surprising number of applications:
- Car Safety - Seat Belts In an accident, the passenger is usually thrown forward. In attempting to restrain this movement, the seat belt gets stretched and, much like an elastic band being pulled, becomes narrower. This is the opposite what you want; in getting narrower, it concentrates all the forces into a much smaller area.
- Construction - Concrete Reinforcement Conventional reinforcements that are used in concrete structures suffer from the fact that as they are loaded in tension, they get thinner. This causes a de-bonding effect, where the reinforcing rod pulls away from the surrounding concrete.
- Health - Dental Floss Auxetic dental floss offers several key benefits, including the ability to expand to fit the widely differing gaps between human teeth and the ability to deliver chemotherapeutics, fluorides or flavors directly to the gum line.
- Manufacturing - Filtration When a conventional net-like material is stretched, the holes close up, whereas in an auxetic version the holes open up. This can be exploited to create a range of objects where controlling the hole size may be important.
- Aerospace - Smart Sensors Smart sensors can be used in a variety of composite structures as in-situ monitoring devices. One of the problems with conventional structures is that when they experience loads or shocks that may have weakened or damaged them, there is rarely any satisfactory method of assessing their integrity.
Materials science is becoming more futuristic every day; check these stories to keep up:
- UM's New Ultrastrong Nanocomposite Nifty new material built in layers like mother of pearl has the strength, if not the ductility, of steel.
- Ice-Nine Modeled In Harvard Computer - We're Doomed It's not quite the world-ending material from Kurt Vonnegut's novel, but Harvard researchers really do think they have found a way for ice to be solid at room temperature.
- Self-Healing Polymer Autonomous Material System Everywhere you look, exposed surfaces are cracking. What if you could have a surface that repaired itself?
Via Zetix Blast-Proof Fabric; lots of good information at the Auxetix website.
(This Science Fiction in the News story used with permission of Technovelgy.com - where science meets fiction